1. Field of the Invention
The present invention relates to a shield for protecting a well head and functional modules of an under sea station from falling objects coming from the surface or during handling from the sea bed or from the surface.
2. Description of the Prior Art
An under sea station for oil working is usually formed from an assembly comprising well heads and modules, such as the connection module (PJU) each ensuring the connection of oil circuits between a well head and a collecting arbor, the peripheral control and checking modules (CJU) and, possibly, the main control module (CSC).
A well head is always provided with a bearing shaft, whereas the modules may comprise, in addition to the central shaft required for handling thereof, two guide columns which serve for pre guiding either the module required for lowering or raising them by means of a string of rods, or the upper module, when two modules are stacked one on the other.
Furthermore, known devices for protecting the under sea installation assembly lack flexibility and are not satisfactory, particularly because they are interlocked with the installation to be protected.
Any object falling towards the shield has a kinetic energy EQU E=1/2mv.sup.2
m being its mass and v its speed.
At the time of the impact, this energy must be absorbed by the shield, without unconsidered stresses F being induced in the structure to be protected. The energy to be absorbed may be considered as the product of a force (less than F,) multiplied by a displacement. Any rapid displacement in the water is hindered by hydrodynamic forces which increase with the square of the speed. It is then difficult, if not impossible, to limit the stresses in the structure to be protected by means of a shield formed from a solid plate. The idea on which the invention is based consists in allowing the displacement, without the formation of high reactive hydro dynamic forces.